1. Technical Field
The present invention relates to a nozzle plate, an inkjet head, and a manufacturing method of the same.
2. Description of the Related Art
Inkjet printing technology has been used mainly in the field of OA (office automation), as well as in industrial fields such as for package marking and printing on clothing. However, with developments in functional ink which includes metal nanoparticles of silver and nickel, etc., the potential applicability of inkjet printing technology has gradually expanded. Current applications of inkjet printing thus include forming circuit patterns in printed circuit boards using functional ink that contains metal nanoparticles.
Continuous developments are currently being made in techniques involving inkjet printing, and in the electronics industry, methods are being studied of utilizing inkjet printing in the manufacture of color filters in liquid crystal displays, and printed circuit boards (PCB's), etc. In contrast to the inkjet technology in the office environment, inkjet methods for industrial use require the operation of all of the multitude of nozzles, formed in the inkjet head in numbers of 128 or 256, etc.
The structure of a typical inkjet head includes a pressure chamber which carries the ink and pressurizes the ink according to changes in its volume, a nozzle connected to a portion of the pressure chamber, a manifold connected to another portion of the pressure chamber which stores the ink supplied to the pressure chamber, and an ink inlet through which ink is supplied to the manifold.
The ink supplied through the ink inlet passes through the manifold and into the pressure chamber, and the ink pressurized in the pressure chamber is ejected out through the nozzle. A piezoelectric component, such as an actuator, etc., is coupled to the pressure chamber to change the volume of the pressure chamber, whereby the ink carried in the pressure chamber can be pressurized.
FIG. 1 is a cross-sectional view of a nozzle plate according to the related art, FIG. 2 is a cross-sectional view of another nozzle plate according to the related art, and FIG. 3 is a diagram illustrating the meniscus of ink ejected from a nozzle plate according to the related art.
The ink from an inkjet head has to be ejected in a stable manner in the form of a complete droplet, in order to obtain a high printing quality. For this, a hydrophobicy treatment may be performed around the exit of the nozzle 102, so that the meniscus 106 of the ink droplet may be formed appropriately.
Without a hydrophobicity treatment, wetting may occur, in which the ink douses the surface of the nozzle 102 exit as it is ejected from the nozzle 102, so that the ink dousing the surface of the nozzle 102 and the ink being ejected form a lump together, causing the ink to be ejected in a flowing manner without achieving a complete droplet. This may result in poor printing quality, and the meniscus 106 formed subsequently after the ejection of ink may also become unstable. Therefore, in order to ensure a level of reliability in an inkjet head, there is a need to perform a hydrophobicity treatment on the surface of the nozzles 102.
Thus, in the past, a hydrophobic layer 104 was formed around the exit of the nozzle 102, as illustrated in FIG. 1, or the hydrophobic layer 104 was formed on the inner surface of the exit of the nozzle 102, as well as around the nozzle 102.
However, when operating an inkjet head, not all of the nozzles 102 in the head are used in ejecting the ink at a particular instance. There may be some nozzles 102 that eject ink, in order to form an image, while there may be some that do not.
For a nozzle 102 through which ink is not ejected, the meniscus 106 may be positioned in the back inside the nozzle 102, as the ink solvent remaining on the nozzle 102 exit vaporizes. When the actuator is operated again to eject ink, this can cause problems in ink ejection, and in sever cases, can cause the ink not to be ejected at all. In particular, if a volatile solvent is used for the ink solvent, the volatile solvent will vaporize faster, so that ink residue may remain inside the nozzle and cause severe problems in ink ejection.
Also, in the case of functional ink containing nanoparticles, as the ink solvent vaporizes, the particles may clog near the nozzle exit, where the particles are in contact with air, so that the nozzle may be blocked.
Furthermore, in the maintenance of an inkjet head, wipers may be used to clean the nozzle portion, and the frequent contact with the wipers can become a cause of abrasion on the nozzles, which may lead to poor printing quality.